Inlining monomorphic calls.

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index 29b28fdb5ec358b9599466cb610f5bda07c947d7..7e7280dffc171bc724521d90aafab86ab4aa0256 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -296,6 +296,10 @@ class Instruction : public ZoneAllocated {
   // Call instructions override this function and return the number of
   // pushed arguments.
   virtual intptr_t ArgumentCount() const = 0;
+  virtual PushArgumentInstr* ArgumentAt(intptr_t index) const {
+    UNREACHABLE();
+    return NULL;
+  };
 
   // Returns true, if this instruction can deoptimize.
   virtual bool CanDeoptimize() const = 0;
@@ -1737,6 +1741,9 @@ class PolymorphicInstanceCallInstr : public TemplateDefinition<0> {
   virtual intptr_t ArgumentCount() const {
     return instance_call()->ArgumentCount();
   }
+  PushArgumentInstr* ArgumentAt(intptr_t index) const {
+    return instance_call()->ArgumentAt(index);
+  }
 
   DECLARE_INSTRUCTION(PolymorphicInstanceCall)
   virtual RawAbstractType* CompileType() const;